ext4: Enable encryption for subpage-sized blocks

Now that we have the code to support encryption for subpage-sized
blocks, this commit removes the conditional check in filesystem mount
code.

The commit also changes the support statement in
Documentation/filesystems/fscrypt.rst to reflect the fact that
encryption on filesystems with blocksize less than page size now works.

[EB: Tested with 'gce-xfstests -c ext4/encrypt_1k -g auto', using the
new "encrypt_1k" config I created.  All tests pass except for those that
already fail or are excluded with the encrypt or 1k configs, and 2 tests
that try to create 1023-byte symlinks which fails since encrypted
symlinks are limited to blocksize-3 bytes.  Also ran the dedicated
encryption tests using 'kvm-xfstests -c ext4/1k -g encrypt'; all pass,
including the on-disk ciphertext verification tests.]

Signed-off-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Link: https://lore.kernel.org/r/20191023033312.361355-3-ebiggers@kernel.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/Documentation/filesystems/fscrypt.rst b/Documentation/filesystems/fscrypt.rst
index 8a0700af959672568b7713dbb6e2f8c82449e200..b0d015a8cdc3aa3d2607d836723664d752540ca3 100644 (file)
--- a/Documentation/filesystems/fscrypt.rst
+++ b/Documentation/filesystems/fscrypt.rst
@@ -331,8 +331,8 @@ Contents encryption
 -------------------
 
 For file contents, each filesystem block is encrypted independently.
-Currently, only the case where the filesystem block size is equal to
-the system's page size (usually 4096 bytes) is supported.
+Starting from Linux kernel 5.5, encryption of filesystems with block
+size less than system's page size is supported.
 
 Each block's IV is set to the logical block number within the file as
 a little endian number, except that:

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 7796e2ffc29425444d7eb65ecf48c88b572b675e..66693510326fa0a9f3c66bc6fae080c10020a19a 100644 (file)
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -4429,13 +4429,6 @@ no_journal:
                }
        }
 
-       if ((DUMMY_ENCRYPTION_ENABLED(sbi) || ext4_has_feature_encrypt(sb)) &&
-           (blocksize != PAGE_SIZE)) {
-               ext4_msg(sb, KERN_ERR,
-                        "Unsupported blocksize for fs encryption");
-               goto failed_mount_wq;
-       }
-
        if (ext4_has_feature_verity(sb) && blocksize != PAGE_SIZE) {
                ext4_msg(sb, KERN_ERR, "Unsupported blocksize for fs-verity");
                goto failed_mount_wq;